1. Field of the Invention
The present invention relates to an anti-reflection plate for a display device such as a CRT (cathode-ray tube), a light emitting diode and the like. More particularly, the invention relates to an anti-reflection plate which is installed in or placed on a screen of the display device to prevent or decrease reflection of external light on the screen and has good abrasion resistance, moisture resistance, and chemical resistance.
2. Description of the Prior Art
When a display device comprising such as a CRT, a light emitting diode, a liquid crystal and a plasma display (e.g., a TV set, a watch or clock, an electronic calculator, etc.) is used in daylight or under lighting, external light reflects on the surface of the screen of the display device or a surface of a transparent plate covering the screen so that the screen has glare, contrast of the displayed image is deteriorated or the image on the screen becomes less visible.
To overcome such problems caused by the reflection of the external light, various anti-reflection plates have been proposed. These anti-reflection plates include the following:
(1) A transparent plate such as a methacrylic resin or glass plate a surface of which is physically or chemically roughened.
This anti-reflection plate has greatly decreased light transmission so that the image on the screen becomes too dark to read even under the normal conditions since unevenness of the screen surface is too deep or the shape of each projection is too sharp. In addition, although the anti-reflection plate can suppress glaring of the screen since it randomly reflects the external light, it cannot decrease the amount of the reflected light so that the surface of the anti-reflection plate becomes light and in turn the image on the screen becomes less visible.
(2) A transparent synthetic resin plate onto which surface unevenness is transferred by means of a physically or chemically roughened glass plate or a roughened roll.
This anti-reflection plate has the same disadvantages as that of the anti-reflection plate (1). Further, it is easily damaged and has poor chemical resistance.
(3) An anti-reflection plate consisting of a mechanically roughened transparent substrate coated with a transparent material to form unevenness on the surface.
Since the mechanically formed unevenness of the substrate is too deep or the shape of each projection is too sharp as described in the above plate (1), the unevenness of the coated material is still deep so that it is very difficult to read the image on the screen of the display device. Furthermore, it is difficult to control the thickness of the coating of the transparent material which reflects the external light.
(4) An anti-reflection plate consisting of a transparent substrate and a coating of a transparent material containing a delustering agent.
This anti-reflection plate has several drawbacks such as whitening of the coating due to a difference in refractive indexes between the coating material and the delustering agent, irregularity or scattering of the unevenness due to sedimentation or agglomeration of the delustering agent.
In addition, any of the conventional anti-reflection plates tends to be easily damaged on its surface, and the damages or flaws on the surface decrease the properties and commercial value of the anti-reflection plates.
As described above, the anti-reflection plate should have the glare shield effect which is achieved by scattering the external light by suitable unevenness of the surface and resolution of the image displayed on the screen of the display device. However, the conventional methods for roughening the surface of the anti-reflection plate are not satisfactory, and the anti-reflection plates are not sufficient from the viewpoint of preventing flaws on the surface.